Photoacoustic tomography (PAT) provides high-resolution biomedical images beyond the optical diffusion limit by combining optical absorption contrast and ultrasonic spatial resolution. To obtain high-quality images, specialized full-ring transducer arrays may be used for full-view detection, but may be relatively expensive compared to linear arrays and may not be as easily integrated with ultrasound systems. The versatility and real-time imaging capability of commercial linear array transducers make them widely used in clinical ultrasound and photoacoustic imaging systems and devices. While commercial linear arrays are readily available, they often suffer from limited-view problems, and the detectable structure is sensitive to the orientations and positions of the probes. For instance, acoustic waves traveling at a grazing angle to the transducer surface are typically difficult to detect.
To overcome this limitation of linear array transducers, many methods have been proposed. One previous method circularly or semi-circularly scanned a linear array to achieve full-view or half-view PAT. However, these methods require time-consuming mechanical scanning. Another method proposed the use of speckle noise to derive PAT. This method required solution of Green's function and has been demonstrated only in simulations to date. Another method utilized artificial backscatters as virtual transducers. However, systems making use of this method still include circular scanning with a single-element transducer, and modeling the backscattered signals may be complicated. Limited-view problems may also be ameliorated using advanced image reconstruction algorithms; however, these image reconstruction methods are typically computationally intensive and time-consuming. In addition, it has been proposed to use acoustic reflectors at either end of, and perpendicular to, a linear array transducer to generate an infinitely wide virtual array, but this method has only been demonstrated in simulations to date
A need exists for a high resolution PAM system that makes use of linear array transducers and other transducer configurations that overcomes the limitations inherent to the transducers without excessive impact on imaging time or requiring computationally challenging image reconstruction methods.